Ceramic processing and design for the direct manufacture of customized labial and lingual orthodontic clear aligner attachments

ABSTRACT

A method of manufacturing pre-formed, customized, ceramic, labial/lingual orthodontic clear aligner attachments (CCAA) by additive manufacturing (AM) may comprise measuring dentition data of a profile of teeth of a patient, based on the dentition data, creating a three dimensional computer-assisted design (3D CAD) model of the patient&#39;s teeth using reverse engineering, and saving the 3D CAD model, designing a 3D CAD structure model for one or more CCAA on various parts of each tooth, importing data related to the 3D CAD CCAA structure model into an AM machine, directly producing the CCAA in the ceramic slurry-based AM machine by layer manufacturing, enabling the provider to deliver patient-specific CCAA&#39;s by an indirect bonding method to the patient&#39;s teeth to improve the efficacy and retention of the clear aligners.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/683,816, filed Jun. 12, 2018, the contents of which are herebyincorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

An embodiment of present invention relates generally to themanufacturing of ceramic labial/lingual orthodontic clear alignerattachments (CCAAs) that create added retention for clear aligners usedfor straightening the teeth and correcting malocclusion. Morespecifically, an embodiment of the invention relates to the methodologyof direct manufacture of customized ceramic labial/lingual orthodonticclear aligner attachments by using a ceramic slurry-based additivemanufacturing (AM) technology.

2. Description of the Related Art

A need arises for more efficient and accurate techniques for creatingcustom lingual and labial ceramic clear aligner attachments, and moreaesthetic labial Clear Aligner Attachments (CAAs). Currently, CAAs fortray aligner treatment are fabricated from a variety of filled andunfilled, shaded, or translucent, bonding materials (such as dentalcomposite) similar to that used to attach conventional orthodontic CAAsto teeth. They are formed by inserting this bonding material into apre-designed and fabricated aligner-like tray that has the attachmentmold included in its shape, and then using a bonding system similar toorthodontic CAA bonding to adhere the CAA to the teeth. This results inexcess bonding material, or “flash” that then needs to be ground offwith a drill in order to assure a proper fit of the subsequentorthodontic aligner trays. During the process of flash removal, oftenthe attachment itself is inadvertently contacted by the drill bit andits shape is mistakenly altered, resulting in an unintentional CAA shapethat doesn't conform as well with the aligner trays.

During the everyday insertion and removal of the aligner trays, the trayabrades the attachment in such a way as to actually alter the CAA'sshape. Often, these attachments must be removed and replaced duringaligner refinement procedures because of the significance of the wear onthe CAA from this insertion and removal abrasion.

During the removal of CAAs made from bonding material, a high speeddrill is utilized to grind off the CAA and remove any residual flashpresent on the tooth surface. This results in enamel also being removedfrom the tooth surface, as it is not within the technical ability of thedentist to adequately discern the boundary between the layer of bondingmaterial and the enamel surface.

There is a need for more efficient and accurate techniques for creatingcustom lingual and labial ceramic clear aligner attachemnsts¹ that aremore easily and accurately placed and more durable during activeorthodontic treatment. After treatment, a more effective removal systemof these attachments would include less polishing of the tooth surfacewith the unwanted side effect of damage to the enamel of the tooth.

SUMMARY OF THE INVENTION

The proposed invention utilizes Ceramic CAAs (CCAAs) that may befabricated by ceramic slurry-based Additive Manufacturing (AM) and maybe bonded to the tooth with an unfilled/filled bonding resin materialalready in use in dentistry. These CCAAs will be placed in an indirecttransfer tray and then bonded to the teeth surfaces utilizing theunfilled or partially filled bonding resin.

An embodiment of the present devices and methods may be used to solveproblems occurring in the current methods of creating resin-based CCAAs.For example, in one embodiment, it may provide a direct manufacturingmethod of customized lingual/labial CCAAs by utilizing any number ofceramic slurry-based AM technologies, examples of which may includedigital light processing (DLP), laser photopolymerizationstereolithography, jet printing (including particle jetting,nanoparticle jetting), layer slurry depositioning (LSD), orlaser-induced slip casting. A slurry is defined as inorganic particlesdispersed in a liquid, and may be photopolymerizable or may polymerizeby other mechanisms. Likewise, similar methods may be used to createmetal CCAAs wherein the inorganic materials in the slurry are metal.Examples of items that may be produced include customized labial/lingualCCAAs according to individual clear aligner (CA) retention needs onindividual teeth, which may have direct tooth-matching retentivefeatures designed into the CCAA base.

The present devices and methods may provide several advantages over thecurrent methodology. 1) The removal of excessive bonding material willbe significantly minimized—less filled resins may be used, which have amuch thinner layer conformation than filled resins. 2) CCAAs will alsoresult in a much more accurate and precise shape versus classicalresin-based CCAAs, as variances in the thickness of the bonding materialwill not be able to result in variances in the shape of the CCAA. 3) TheCCAA will not be able to be inadvertently damaged or altered in itsshape by the post-placement flash polishing procedure because there willbe less flash and the ceramic material of which the OA is fabricatedwill be resistant to indentation by accidental contact with the drillduring the polishing/flash removal process. The CCAA will be more exactin its shape because it will be formed first, by Additive Manufacturing(AM), and then may be adhered with a thinner adhesive. This results inless variability of shape than the current procedures where thetechnique of placement can greatly vary the shape of the OA. 5) Mostimportantly, the OA will not be susceptible to deformation in shape dueto abrasion from constant insertion and removal of the aligner traysbecause the ceramic OA is much more resistant to abrasion.

For example, in an embodiment, a method of manufacturing pre-formed,customized, ceramic, labial/lingual orthodontic clear alignerattachments (CCAA) by additive manufacturing (AM) may comprise measuringdentition data of a profile of teeth of a patient, based on thedentition data, creating a three dimensional computer-assisted design(3D CAD) model of the patient's teeth using reverse engineering, andsaving the 3D CAD model, designing a 3D CAD structure model for one ormore CCAA on various parts of each tooth, importing data related to the3D CAD CCAA structure model into an AM machine, directly producing theCCAA in the ceramic slurry-based AM machine by layer manufacturing toform a patient-specific CCAA by an indirect bonding method, thepatient-specific CCAA adapted to the patient's teeth.

In embodiments, the additive manufacturing machine may use aslurry-based process. The slurry-based process may include at least oneof lithography-based manufacturing, inkjet printing, slip casting, laserlithography additive manufacturing, direct light processing, andselective laser melting. The CCAA may be made of an inorganic materialwith at least one component selected from a group of materials includingan oxide ceramic, a nitride ceramic, a carbide ceramic, Aluminum Oxide(Al2O3), Zirconium Oxide (ZrO2), Alumina-toughened Zirconia (ATZ),Zirconia-toughened alumina (ZTA), Lithium disilicate, Leucite silicateand Silicon Nitride. The 3D CAD CCAA structure model may include datadefining a fracture wall around a perimeter of a base of the CCAA. Thefracture wall may have a thickness of about 10-about 150 μm, inclusive.The fracture wall may be adapted provide predictable fracture of thewall upon application of the normal force, enabling debonding of theCCAA through a combination of tensile and peeling forces. The normalforce may be applied in at least one of a mesial-distal direction, anocclusal-gingival direction, or to any opposite corners. The combinationof tensile and peeling forces may be less than a shear bond strength ofa bonded CCAA. The 3D CAD CCAA structure model may include datarepresenting at least a) the CCAA base (bonding area) that has recessesand/or undercuts into the bonding surface of the CCAA that arecustom-shaped to fit the negative of a labial/lingual tooth surface, andcontact a particular area of a tooth surface, c) a CCAA material, d) theparticular tooth's profile, and e) a CCAA guide or indirect bonding jigto guide 3-dimensional placement of the CCAA onto the tooth. The ceramicslurry-based AM machine may comprise a molding compartment comprising aplatform and a plunger to directly produce the CCAA by layermanufacturing, a material compartment, and an LED light source fordigital light processing, wherein the CCAA is produced by layermanufacturing using slicing software to separate the 3D CAD CCAAstructure model into layers and to get a horizontal section model foreach layer so that a shape of each layer produced by the ceramicslurry-based AM machine is consistent with the 3D CAD structure data.

The ceramic slurry-based AM machine may comprise a vat adapted to holdthe CCAA during manufacturing, a horizontal build platform adapted to beheld at a settable height above the vat bottom, an exposure unit,adapted to be controlled for position selective exposure of a surface onthe horizontal build platform with an intensity pattern withpredetermined geometry, a control unit, adapted to receive the 3D CADCCAA structure model and, using the 3D CAD CCAA structure model to:polymerize in successive exposure steps layers lying one above the otheron the build platform, respectively with predetermined geometry, bycontrolling the exposure unit, and to adjust, after each exposure stepfor a layer, a relative position of the build platform to the vatbottom, to build up the object successively in the desired form, whichresults from the sequence of the layer geometries. The exposure unit mayfurther comprise a laser as a light source, a light beam of whichsuccessively scans the exposure area by way of a movable mirrorcontrolled by the control unit.

Directly producing the CCAA by layer manufacturing may further comprisein an apparatus comprising: a vat with an at least partiallytransparently or translucently formed horizontal bottom, into whichlight polymerizable material can be filled, a horizontal build platformadapted to be held at a settable height above the vat bottom, anexposure unit adapted to be controlled for position selective exposureof a surface on the build platform with an intensity pattern withpredetermined geometry, comprising a light source refined bymicromirrors to more precisely control curing, a control unit adaptedfor polymerizing in successive exposure steps layers lying one above theother on the build platform, controlling the exposure unit so as toselectively expose a photo-reactive slurry in the vat, adjusting, aftereach exposure for a layer, a relative position of the build platform tothe vat bottom, and building up the CCAA successively in the desiredform, resulting from the sequence of the layer geometries. The exposureunit may further comprise a laser as a light source, a light beam ofwhich successively scans the exposure area by way of a movable mirrorcontrolled by the control unit.

A scanning accuracy may be less than 0.02 mm. A manufacturing accuracyin the z-axis of the ceramic slurry-based AM machine may be from 5 toabout 60 μm, and wherein the accuracy is achieved by using a betweenlayer additive error compensation method based on an amount ofpolymerization shrinkage, to prevent errors in the CCAA base morphology.Manufactured layers of the CCAA may comprise a material selected fromthe group consisting of high strength oxide ceramics including AluminumOxide (Al2O3) and Zirconium Oxide (ZrO2) and may be mono- orpolycrystalline filled ceramic. The CCAA may less than 4.00 mm thickfrom the nearest tooth bonding surface to its outer edges. The 3D CADmodel may be saved as a 3D vector file format. The thickness of themanufactured layers is from 5 to 100 micrometers (μm) based on theresolution requirements of the CCAA for proper retention to the clearaligner. Different light curing strategies (LCSs) and depths of cure(Cd) are used. A selection of glass or oxide ceramic filler material forproducing layers of the CCAA is based on different force demands.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary flow diagram of an embodiment of a process fordirect manufacturing of lingual or labial orthodontic attachments orattachment brackets.

FIG. 2 illustrates an example of an orthodontic attachment.

FIG. 3 is an exemplary illustration of an embodiment of an orthodonticattachment.

FIG. 4 illustrates an example of a single attachment on a lower premolarmolar tooth.

FIG. 5 is an exemplary block diagram of a computer system in whichembodiments of the present systems and method may be implemented.

FIGS. 6a, 6b, and 6c are exemplary illustrations of an embodiment of aCCAA with fracture groove.

FIGS. 7a and 7b are exemplary illustrations of an embodiment of a CCAAwith fracture groove.

FIGS. 8a and 8b are exemplary illustrations of an embodiment of anorthodontic attachment and retentive features.

FIGS. 9a and 9b illustrate a base view of an example single attachmentwith and without retentive structures.

FIG. 10 is an exemplary illustration of an embodiment of an orthodonticattachment.

FIGS. 11a, 11b, and 11c are exemplary illustrations of an embodiment ofan indirect bonding jig for orthodontic attachments.

FIGS. 12a and 12b are exemplary illustrations of an embodiment of anorthodontic attachment bracket.

FIG. 13 is an exemplary illustration of an embodiment of an orthodonticattachment.

FIG. 14 is an exemplary illustration of an embodiment of orthodonticattachments.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention provides improved techniques forcreating custom lingual or labial CCAAs.

An exemplary flowchart of an embodiment a direct manufacturing process100 of lingual or labial orthodontic CCAAs by digital light processingis shown in FIG. 1. The process begins with 102, in which dentition datais measured and the parameters of the tooth profile are analyzed. Forexample, such measurement may use CT layer scanning a non-contact 3Dscanner or an intra-oral scanner directly on the patient's teeth, or mayuse 3D readings on a teeth model previously cast or 3D printed using acoordinate measuring machine, a laser scanner, or a structured lightdigitizers. The scanning accuracy of such techniques is typically lessthan 0.02 mm. A manufacturing accuracy in the z-axis of the ceramicslurry-based AM machine may be from 5 to about 60 μm, and wherein theaccuracy may be achieved by using a between layer additive errorcompensation method that predicts an amount of polymerization shrinkage.

In 104, based on the given dentition data, a 3D CAD model of themeasured teeth is constructed based on the dentition data and saved inthe computer in a typical file format, such as the .stl file format. Theexterior structure of teeth is complicated, usually including irregularcurves. The software may then be used to re-arrange the teeth in themodel to the desired treatment outcomes that may be based on thelong-axis of a tooth.

In 106, additional information, such as the desired shape and toothlocation of the CCAAs are determined.

In 108, the CCAA is designed by the software or chosen from a list ofoptions by the clinician based on the input 3D CAD model of the measuredteeth, the model of the desired treatment outcomes, and the anticipatedlimitations of the CA and its ability to track on the teeth throughouttreatment. The output of the design process may be a 3D CAD model. Sucha 3D CAD model may be designed for a single lingual/labial CCAAstructure, including the indirect bonding (IDB) tray.

3D CAD CCAA structure models of labial or lingual CCAAs may be designedby computer according to the orthodontic requirements, CA materialconsiderations, and teeth morphology.

3D CAD CCAA structure models are processed to generate manufacturingcontrol data for use by the production equipment. For example, whereceramic slurry-based AM equipment is used to produce the CCAAs, thesoftware slices the 3D CAD CCAA structure models to separate it intothin layers and get the horizontal section model for each layer. Basedon this section model, the ceramic slurry-based AM equipment candirectly produce CCAAs, ensuring the shape of each layer is consistentto the 3D CAD structure data. For example, the thickness of such layersmay be about 20 μm to about 50 μm (micrometers or microns) with amanufacturing accuracy of about 5 μm to about 60 μm by usingbetween-layer additive error compensation.

Returning to 108 of FIG. 1, the 3D CAD CCAA structure model istransmitted to or imported into a ceramic slurry-based AM machine, suchas a DLP machine and the ceramic CCAAs are produced. In the case of AMDLP or another ceramic slurry-based AM procedure, the CCAA may beproduced by digital light processing directly.

Digital light processing (DLP) is another 3D additive manufacturing (AM)process that works by stacking layers of a photocurable resin with anAluminum Oxide (Al₂O₃) or Zirconium Oxide (ZrO₂) solid loading, andfollowed by a thermal debinding and sintering step. The higherresolution of this process is made possible by the LED light's digitalmirror device (DMD) chip and optics used. Lithography-based ceramicmanufacturing (LCM) has improved this process making it more accuratewith higher resolution (40 μm) and rigidity. The new LCM processinvolves the selective curing of a photosensitive resin containinghomogenously dispersed oxide or glass ceramic particles that can befabricated at very high resolution due to imaging systems which enablethe transfer of layer information by means of ever-improving LEDtechnology.

In 110, post-processing may then be applied. For example, a thermaltreatment (for binder burnout) and a sintering process may be applied toachieve optimal or improved ceramic density. For example, the debindingand sintering phase may include removing the green CCAA from the device,exposing the blank to a furnace to decompose the polymerized binder(debinding), and sintering of the ceramic material.

Examples of raw materials of the CCAAs may include powder of highstrength oxides, nitrides and carbides ceramics including but notlimited to: Aluminum Oxide (Al2O3), Zirconium Oxide (ZrO2), Aluminatoughened Zirconia (ATZ), Zirconia-toughened alumina (ZTA),Lithiumdisilicate, Leucitesilicate, Nitrides (e.g. SiN4), and mono- orpolycrystalline ceramic. The base of CCAA may be adhered to the toothsurface and the CCAA surface may be matched to matching indentationswithin the CA. According to requirements of mechanical properties,different composition of material may be required for the layers duringthe DLP manufacturing process. After being built up, the CCAAs may havea gradient and better performance.

Further, the CCAA surface may be processed based on clinical demand.

In 112, the CCAA is ready to be placed.

FIG. 2 depicts an orthodontic attachment, such as a CCAA, where the baseof the attachment may be the surface that contacts the tooth and theface of the attachment may include any surface that contacts thealigner.

Typically, the thickness 202 of the CCAA pad 204 may extend less than2.0 mm for lingual CCAAs and less than 2.5 for labial CCAAs from thesurface of the tooth, with a labial and lingual minimum extension of0.25 mm. The CCAA pad 204 may be adhered to the tooth surface withwell-known dental adhesives that may be unfilled dental resins orpartially filled dental resins. Depending upon the manufacturing processused, different ceramics or composition of powder may be required forthe layers. For example, if a selective laser melting manufacturingprocess is used, an LED light source may be used for the selectivecuring of a photosensitive resin containing the oxide or glass ceramicparticles. Different layers may use different ceramics or compositionsof powder.

The CCAA pad 204, which holds or connects the CCAA to the tooth surface,may be designed specifically according to the tooth surface profile,instead of a generalized gridding pattern. The customized CCAAs can meetindividual case demand, such as increased vertical tracking for upperlateral incisors or for lower premolars to level the curve of Spee orreduce overbite. For example, as shown in FIG. 14, the curve on toothsurface and the designed CCAA, the tooth side of the CCAA (CCAA pad) ismatched to the lingual or labial surface of the tooth, for example forlingual CCAA 1402 and labial CCAA 1404. FIG. 14 depicts two orthodonticattachments 1402, 1404 bonded to a tooth where the opposing directionsof the attachments aids in creating lingual crown torque tooth and whereflipping the axis of the attachments would result in labial crowntorque. The specific angle of the retentive edge 1406, 1408 andlocations of the attachments optimize the torqueing moment on the tooth.In this example, orthodontic attachment 1402 has −8 degrees of torqueand orthodontic attachment 1404 has +8 degrees of torque. Theorthodontic aligner may place a force on each retentive end tofacilitate the motion. The trapezoidal shape of the aligner may ensureone edge is always acting like a retentive feature to hold the alignerto the arch.

FIG. 8 depicts an example of retentive structures 702 designed into thebase of attachment 700 base. These retentive structures 702 may be ofany shape that is a three-dimensional FIG. 800 with a positive draftangle 802 greater than 0, as shown in FIG. 8b . Other examples ofretentive structures other than semi-lunar cones may includefull-circles, squares, rectangles, any variety of retentive lattices ormeshes—all shapes that at some point would have a positive draft angleand would therefore be more efficiently manufactured via 3DP vsinjection molding.

The neutral plane of the draft may be oriented towards the toothstructure and may be flat or itself contoured to the shape of the toothsurface to which it is meant to be bonded. While any degree of retentionwould achieve the intended retentive interaction with bonding cement, arange of designed draft angles may be utilized to compensate for thelimitations of a specific 3D printing process.

FIG. 3 depicts a thin fracture wall 302 around the attachment 300 base,which has a thickness 304 of about 10 to about 150 μm, inclusive.Bonding cement may be inserted into the cavity formed by the thinfracture wall. The wall thickness may consistent around all edges of theattachment enabling a normal force to be applied in any direction(mesial-distal, occlusal-gingival, or to any opposing corners). Thecontinuity of the wall around the entire attachment 300 may enablepredictable fracture of the wall via pliers in any direction, enablingdebonding of the attachment 300 through a combination of tensile andpeeling forces.

FIG. 4 depicts an attachment 400 with its base 402 contoured to theshape of the tooth. The contouring may match the desired position of theattachment on the tooth. Any changes in the attachment's positioningwould reflect changes in the contouring. The base and the face arecontoured to the tooth.

FIG. 9a depicts the retentive structures, such as 902, contoured to thetooth surface looking from the inside of a tooth 3D vector (.stl) shell.Each structure may be contoured to fit its corresponding area of toothsurface within the attachment position. The attachment base cavity 952shown in FIG. 9b may also be contoured to ensure each retentivestructure maintains its dimensions and all structures have a similardepth.

FIG. 6a depicts an example of a fracture groove 602 within the middlevertical third of a ceramic attachment 600 viewed from the attachment'sbase. FIG. 6b depicts an example of an auxiliary fracture groove 632within the middle vertical third of a ceramic attachment 630 viewed fromthe attachment's face. FIG. 6c . depicts the attachment 670 split intothirds with the fracture groove 672 and auxiliary fracture groove 674within the middle third 676 of the attachment, between the mesial third678 and distal third 680, viewed from the attachment's face. Therespective ratios for the fracture and auxiliary fracture groovedistances from the mesial and distal edges may be variable.

A side view of an exemplary printed CCAA 700 is shown in FIGS. 7a and 7b. The pad 706 of the CCAA may highly match the tooth surface andmaximize the tooth contact surface. This may allow for more accurateCCAA placement by the clinician and better bond approximation to thetooth. FIG. 7a depicts the weakened area consisting of a tooth curveddepression 702 (groove) in the attachment base running vertically(occlusal-gingival) within the middle third of the attachment, as inFIGS. 6a and 6c . The attachment area 704 between the fracture grooveand auxiliary fracture groove features may form the attachment'sweakened area.

Finite-element analysis has revealed that mesial-distal forces on thesides of the attachment result in a concentration of forces in themiddle third of the attachment base. The groove is defined as the areaof removed material from where forces would have been most concentrated.The addition of this “groove” lowers the forces required to predictablycreate an attachment fracture down the middle vertical third of theattachment, which aids in debonding the ceramic attachment from thetooth. The weakened area, and the fracture force may be optimized byadjusting the dimensions of the fracture groove and/or the auxiliaryfracture groove.

As shown in FIG. 7a , groove 702 may be consistent in depth from thetooth surface, matching the contour of the tooth. Likewise, as shown inFIG. 7b , groove 708 may be variable in distance from the tooth surface.In either embodiments, the groove depth may be a nominal value for allattachments or may vary based on the attachment width. In instanceswhere the groove is a nominal value, the groove depth may be in a rangeof 0.10 mm to 1.0 mm. In instances where the groove depth is variable,it may have a range of 1-50% of the width.

CCAA 600 may further include an attachment such as a hook 1002, shown inFIG. 10 that provides the capability to use additional delivery systemssuch as elastomers, springs or other attachments that create vectors offorce. The example shown in FIG. 10 depicts an orthodontic attachmentwith a distal gingival hook. The hook may be used for any form oforthodontic elastics to aid in the treatment of malocclusion. In anumber of embodiments, these features may be manufactured as one piece,protruding from any predesigned area to create the proper force vectorsdesired, and no machining of the features is required to produce asuitable CCAA.

FIGS. 11a, 11b, 11c depict an exemplary orthodontic aligner 1100 thataccommodates an orthodontic attachment 1102, 1104, 1106 with any givenshape. Only one exemplary shape is depicted in this image, but thepresent devices and methods are applicable to any shape. The attachmentindentation fits over and completely encases the attachment to aid inmovement. The aligner may be easily pulled over the attachment forremoval.

FIGS. 12a and 12b depict exemplary orthodontic attachments that may beused in combination aligner-bracket treatment. FIG. 12a depicts severalviews of an exemplary attachment 1200 with a curved slot 1202 that canaccommodate a standard orthodontic wire. This example shows a ribbonwire configuration, whereby the archwire is longer vertically thanhorizontally. FIG. 12b depicts several views of an exemplary attachmenttube 120 that may be placed on teeth for the purposes of accepting awire to move teeth with or without a clear aligner. The channel 1212 maypass mesial-distal and may be consistent in cross-sectional measurement,which may be of a circular, rectangular (in this example) or square incross-sectional design, with square and rectangular cross-sectionshaving slightly rounded corners of a chosen radius. Regardless of theshape, in embodiments, the average cross-section of the tube may be nogreater than 0.50 mm².

FIG. 13 depicts several views of an exemplary orthodontic attachment1300 that may be used to aid in tipping, torqueing, or rotating thetooth. Half of the attachment retaining edge 1302 is on one side whilethe other half 1304 is on the opposing side. The location and angle theattachment is placed on the tooth may determine the force placed on eachretaining edge. This action may not only aid in tooth movement but mayremain an active measure in retaining the aligner on the arch.

Using the ceramic slurry-based AM technique can turn the designed modelinto a ceramic product rapidly. The CCAA manufacturing involves fewsteps and can be done on site, saving time and cost.

The described techniques may be used to manufacture CCAAs from variousOxide ceramics and light-curable materials such as Aluminum Oxide(Al₂O₃) and Zirconium Oxide (ZrO₂).

Many patients desire a CCAA that matches the color of the tooth to whichthe CCAA is attached. As another example, embodiments of the presentinvention may provide the capability to produce translucent CCAAs, whichmay provide still improved appearance. Additionally, embodiments of thepresent invention may provide the capability to produce CCAAs in a shadeclosely matched to the patient's tooth shades, which may be the sameshade or matched to individual teeth as the tooth shades vary.

The described techniques may be made cost-effective to the point wherean individual orthodontic practice could purchase the required equipmentand software.

Ceramic slurry-based AM has many advantages for orthodontic CCAAfabrication over selective laser sintering/melting (SLM) which usesthermal energy, and 3-D printing (3DP) systems that use a binder andpolymer-derived ceramics (PDCs). For example, ceramic slurry-based AMmay provide higher surface quality, better object resolution, andimproved mechanical properties. PDCs structured using light in astereolithographic or mask exposure process may also be used as aceramic AM method for CCAA fabrication.

Custom lingual CCAAs may be fabricated by this method, which may receivea pre-bent customized archwire as described by US 2007/0015104 A1.Custom labial CCAAs may also receive pre-bent wires.

The procedure for the layering additive manufacturing (AM) methodologyof the labial/lingual orthodontic CCAAs by ceramic slurry-based Amiss asfollows.

An example of ceramic slurry-based AM is the lithography-based digitallight processing (DLP) technique described in U.S. Pat. No. 8,623,264B2, which is incorporated herein by reference, but may be brieflysummarized as follows: a light-polymerizable material, the materialbeing located in at least one trough, having a particularlylight-transmissive, horizontal bottom, is polymerized by illumination onat least one horizontal platform, the platform having a pre-specifiedgeometry and projecting into a trough, in an illumination field, whereinthe platform is displaced vertically to form a subsequent layer,light-polymerizable material is then added to the most recently formedlayer, and repetition of the foregoing steps leads to the layeredconstruction of the orthodontic CCAA in the desired prescription/mold,which arises from the succession of layer geometries determined from theCAD software. The trough can be shifted horizontally to a supplyposition, and the supply device brings light-polymerizable material atleast to an illumination field of the trough bottom, before the at leastone trough is shifted to an illumination position in which theillumination field is located below the platform and above theillumination unit, and illumination is carried out, creating a “greenCCAA”.

The light-polymerizable material or photo-reactive suspension (slurry)can be prepared based on commercially available di- and mono-functionalmethacrylates. An example material might be a slurry blend of 0.01-0.025wt % of a highly reactive photoinitiator, 0.05-6 wt % a dispersant, anabsorber, and 2-20 wt % of a non-reactive diluent. A solid loading ofhigh strength Oxide ceramics such as Aluminum Oxide (Al₂O₃) andZirconium Oxide (ZrO₂) powder can be used, but this process may extendto other ceramic materials.

An exemplary block diagram of a computer system 700, in which theprocesses shown above may be implemented, is shown in FIG. 7. Computersystem 700 is typically a programmed general-purpose computer system,such as a personal computer, workstation, server system, andminicomputer or mainframe computer. Computer system 700 includes one ormore processors (CPUs) 702A-702N, input/output circuitry 704, networkadapter 706, and memory 708. CPUs 702A-702N execute program instructionsin order to carry out the functions of embodiments of the presentinvention. Typically, CPUs 702A-702N are one or more microprocessors,such as an INTEL PENTIUM® processor. FIG. 7 illustrates an embodiment inwhich computer system 700 is implemented as a single multi-processorcomputer system, in which multiple processors 702A-702N share systemresources, such as memory 708, input/output circuitry 704, and networkadapter 706. However, the present invention also contemplatesembodiments in which computer system 700 is implemented as a pluralityof networked computer systems, which may be single-processor computersystems, multi-processor computer systems, or a mix thereof.

Input/output circuitry 704 provides the capability to input data to, oroutput data from, computer system 700. For example, input/outputcircuitry may include input devices, such as keyboards, mice, touchpads,trackballs, scanners, etc., output devices, such as video adapters,monitors, printers, etc., and input/output devices, such as, modems,etc. Network adapter 706 interfaces device 700 with a network 710.Network 710 may be any public or proprietary LAN or WAN, including, butnot limited to the Internet.

Memory 708 stores program instructions that are executed by, and datathat are used and processed by, CPU 702 to perform the functions ofcomputer system 700. Memory 708 may include, for example, electronicmemory devices, such as random-access memory (RAM), read-only memory(ROM), programmable read-only memory (PROM), electrically erasableprogrammable read-only memory (EEPROM), flash memory, etc., andelectro-mechanical memory, such as magnetic disk drives, tape drives,optical disk drives, etc., which may use an integrated drive electronics(IDE) interface, or a variation or enhancement thereof, such as enhancedIDE (EIDE) or ultra-direct memory access (UDMA), or a small computersystem interface (SCSI) based interface, or a variation or enhancementthereof, such as fast-SCSI, wide-SCSI, fast and wide-SCSI, etc., orSerial Advanced Technology Attachment (SATA), or a variation orenhancement thereof, or a fiber channel-arbitrated loop (FC-AL)interface.

The contents of memory 708 varies depending upon the function thatcomputer system 700 is programmed to perform. In the example shown inFIG. 7, memory contents that may be included in a system in which acontent analysis platform is implemented are shown. However, one ofskill in the art would recognize that these functions, along with thememory contents related to those functions, may be included on onesystem, or may be distributed among a plurality of systems, based onwell-known engineering considerations. Embodiments of the presentinvention contemplate any and all such arrangements.

In the example shown in FIG. 7, memory 708 may include dentition datameasurement routines 712, 3D CAD teeth model construction routines 714,3D CAD teeth model editing routines 716, CCAA design routines 718,manufacturing control data generation routines 720, and operating system722. Dentition data measurement routines 712 may obtain and processdentition data, such as may be generated by CT layer scanning or anon-contact 3D scanner directly on the patient's teeth, or uses 3Dreadings on the teeth model previously cast. 3D CAD teeth modelconstruction routines 714 may construct a 3D CAD model of the measuredteeth based on the dentition data. 3D CAD teeth model editing routines716 may be used to re-arrange the teeth in the model to the desiredtreatment outcomes and may additionally be used to accept additionalinformation, such as the desired torque, offset, angulation of selectCCAAs and occlusal/incisal coverage for placement guide. CCAA designroutines 718 may be used to design and generate a 3D CAD model based onthe input 3D CAD model of the measured teeth, the model of the desiredtreatment outcomes, and the input additional information. Manufacturingcontrol data generation routines 720 may be used to generatemanufacturing control data for use by the production equipment.Operating system 722 provides overall system functionality.

As shown in FIG. 7, an embodiment of the present invention contemplatesimplementation on a system or systems that provide multi-processor,multi-tasking, multi-process, and/or multi-thread computing, as well asimplementation on systems that provide only single processor, singlethread computing. Multi-processor computing involves performingcomputing using more than one processor. Multi-tasking computinginvolves performing computing using more than one operating system task.A task is an operating system concept that refers to the combination ofa program being executed and bookkeeping information used by theoperating system. Whenever a program is executed, the operating systemcreates a new task for it. The task is like an envelope for the programin that it identifies the program with a task number and attaches otherbookkeeping information to it. Many operating systems, including Linux,UNIX®, OS/2®, and Windows®, are capable of running many tasks at thesame time and are called multitasking operating systems. Multi-taskingis the ability of an operating system to execute more than oneexecutable at the same time. Each executable is running in its ownaddress space, meaning that the executables have no way to share any oftheir memory. This has advantages, because it is impossible for anyprogram to damage the execution of any of the other programs running onthe system. However, the programs have no way to exchange anyinformation except through the operating system (or by reading filesstored on the file system). Multi-process computing is similar tomulti-tasking computing, as the terms task and process are often usedinterchangeably, although some operating systems make a distinctionbetween the two.

It is important to note that while aspects of the present invention maybe implemented in the context of a fully functioning data processingsystem, those of ordinary skill in the art will appreciate that theprocesses of an embodiment of the present invention are capable of beingdistributed in the form of a computer program product including acomputer readable medium of instructions. Examples of non-transitorycomputer readable media include storage media, examples of whichinclude, but are not limited to, floppy disks, hard disk drives,CD-ROMs, DVD-ROMs, RAM, and, flash memory.

Although specific embodiments of the present invention have beendescribed, it will be understood by those of skill in the art that thereare other embodiments that are equivalent to the described embodiments.Accordingly, it is to be understood that the invention is not to belimited by the specific illustrated embodiments, but only by the scopeof the appended claims.

What is claimed is:
 1. A method of manufacturing pre-formed, customized,ceramic, labial/lingual orthodontic clear aligner attachments (CCAA) byadditive manufacturing (AM), said method comprising: measuring dentitiondata of a profile of teeth of a patient; based on the dentition data,creating a three dimensional computer-assisted design (3D CAD) model ofthe patient's teeth using reverse engineering, and saving the 3D CADmodel; designing a 3D CAD structure model for one or more CCAA onvarious parts of each tooth; importing data related to the 3D CAD CCAAstructure model into an AM machine; directly producing the CCAA in theceramic slurry-based AM machine by layer manufacturing to form apatient-specific CCAA by an indirect bonding method, thepatient-specific CCAA adapted to the patient's teeth.
 2. The method ofclaim 1, wherein the additive manufacturing machine uses a slurry-basedprocess.
 3. The method of claim 2, wherein the slurry-based processincludes at least one of lithography-based manufacturing, inkjetprinting, slip casting, laser lithography additive manufacturing, directlight processing, and selective laser melting.
 4. The method of claim 1,wherein the CCAA is made of an inorganic material with at least onecomponent selected from a group of materials including an oxide ceramic,a nitride ceramic, a carbide ceramic, Aluminum Oxide (Al2O3), ZirconiumOxide (ZrO2), Alumina-toughened Zirconia (ATZ), Zirconia-toughenedalumina (ZTA), Lithium disilicate, Leucite silicate and Silicon Nitride.5. The method of claim 1, wherein the 3D CAD CCAA structure modelincludes data defining a fracture wall around a perimeter of a base ofthe CCAA.
 6. The method of claim 5, wherein the fracture wall has athickness of about 10-about 150 μm, inclusive.
 7. The method of claim 6,wherein the fracture wall is adapted provide predictable fracture of thewall upon application of the normal force, enabling debonding of theCCAA through a combination of tensile and peeling forces.
 8. The methodof claim 7, wherein the normal force is applied in at least one of amesial-distal direction, an occlusal-gingival direction, or to anyopposite corners.
 9. The method of claim 8, wherein the combination oftensile and peeling forces is less than a shear bond strength of abonded CCAA.
 10. The method of claim 1, wherein the 3D CAD CCAAstructure model includes data representing at least a) the CCAA base(bonding area) that has recesses and/or undercuts into the bondingsurface of the CCAA that are custom-shaped to fit the negative of alabial/lingual tooth surface, and contact a particular area of a toothsurface, c) a CCAA material, d) the particular tooth's profile, and e) aCCAA guide or indirect bonding jig to guide 3-dimensional placement ofthe CCAA onto the tooth.
 11. The method of claim 1, wherein the ceramicslurry-based AM machine comprises: a molding compartment comprising aplatform and a plunger to directly produce the CCAA by layermanufacturing; a material compartment; and an LED light source fordigital light processing, wherein the CCAA is produced by layermanufacturing using slicing software to separate the 3D CAD CCAAstructure model into layers and to get a horizontal section model foreach layer so that a shape of each layer produced by the ceramicslurry-based AM machine is consistent with the 3D CAD structure data.12. The method of claim 1, wherein the ceramic slurry-based AM machinecomprises: a vat adapted to hold the CCAA during manufacturing; ahorizontal build platform adapted to be held at a settable height abovethe vat bottom; an exposure unit, adapted to be controlled for positionselective exposure of a surface on the horizontal build platform with anintensity pattern with predetermined geometry; a control unit, adaptedto receive the 3D CAD CCAA structure model and, using the 3D CAD CCAAstructure model to: polymerize in successive exposure steps layers lyingone above the other on the build platform, respectively withpredetermined geometry, by controlling the exposure unit, and to adjust,after each exposure step for a layer, a relative position of the buildplatform to the vat bottom, to build up the object successively in thedesired form, which results from the sequence of the layer geometries.13. The method of claim 12, wherein the exposure unit further comprisesa laser as a light source, a light beam of which successively scans theexposure area by way of a movable mirror controlled by the control unit.14. The method of claim 1, wherein directly producing the CCAA by layermanufacturing further comprises: in an apparatus comprising: a vat withan at least partially transparently or translucently formed horizontalbottom, into which light polymerizable material can be filled, ahorizontal build platform adapted to be held at a settable height abovethe vat bottom, an exposure unit adapted to be controlled for positionselective exposure of a surface on the build platform with an intensitypattern with predetermined geometry, comprising a light source refinedby micromirrors to more precisely control curing, a control unit adaptedfor polymerizing in successive exposure steps layers lying one above theother on the build platform; controlling the exposure unit so as toselectively expose a photo-reactive slurry in the vat; adjusting, aftereach exposure for a layer, a relative position of the build platform tothe vat bottom; and building up the CCAA successively in the desiredform, resulting from the sequence of the layer geometries.
 15. Themethod of claim 14, wherein the exposure unit further comprises a laseras a light source, a light beam of which successively scans the exposurearea by way of a movable mirror controlled by the control unit.
 16. Themethod of claim 15, wherein a scanning accuracy (trueness, per tooth) isless than 0.025 mm and the precision is less than 0.100 mm.
 17. Themethod of claim 14, wherein a manufacturing accuracy in the z-axis ofthe ceramic slurry-based AM machine is from 5 to about 60 and whereinthe accuracy is achieved by using a between layer additive errorcompensation method based on a calculated amount of polymerizationshrinkage, to prevent errors in the CCAA base morphology.
 18. The methodof claim 14, wherein manufactured layers of the CCAA comprise a materialselected from the group consisting of high strength oxide ceramicsincluding Aluminum Oxide (Al₂O₃) and Zirconium Oxide (ZrO₂) and may bemono- or polycrystalline filled ceramic.
 19. The method according toclaim 14, wherein the CCAA is less than 3.00 mm thick from the nearesttooth bonding surface to its outer edges.
 20. The method of claim 1,wherein the 3D CAD model is saved as a 3D vector file format.
 21. Themethod of claim 1, wherein the thickness of the manufactured layers isfrom 5 to 100 micrometers (μm) based on the resolution requirements ofthe CCAA for proper retention to the clear aligner.